1. Field of the Invention
The present invention relates to a process for preparing a catalyst used in producing methacrylic acid by the gas-phase catalytic oxidation of methacrolein.
2. Description of the Prior Art
Hitherto, a large number of catalysts containing phosphorus, molybdenum and bismuth have been reported as a catalyst for producing methacrylic acid by the gas-phase catalytic oxidation of methacrolein, for example, as shown in Japanese Patent Application Kokai No. 48-64017, No. 52-33615, No. 52-33616, No. 52-91821 and No. 53-7616. However, so far as the technical contents of these patents are looked over, every catalyst has defects that the result of reaction is poor, the catalytic activity largely lowers with the lapse of time, and the preparation of the catalyst lacks reproducibility, so that it is not said to be satisfactory as industrial catalysts. At present, therefore, a further improvement is being desired.